feat(auth): add signInUseCase (test red until DI lands)

packages/auth/src/application/use-cases/sign-in.use-case.ts

@@ -0,0 +1,34 @@
+import { AuthenticationError } from "../../entities/errors";
+import type { Cookie } from "../../entities/cookie";
+import type { Session } from "../../entities/session";
+import { authContainer } from "../../di/container";
+import { AUTH_SYMBOLS } from "../../di/symbols";
+import type { IUsersRepository } from "../repositories/users-repository.interface";
+import type { IAuthenticationService } from "../services/authentication-service.interface";
+
+export async function signInUseCase(input: {
+  username: string;
+  password: string;
+}): Promise<{ session: Session; cookie: Cookie }> {
+  const usersRepository = authContainer.get<IUsersRepository>(
+    AUTH_SYMBOLS.IUsersRepository,
+  );
+  const authService = authContainer.get<IAuthenticationService>(
+    AUTH_SYMBOLS.IAuthenticationService,
+  );
+
+  const existingUser = await usersRepository.getUserByUsername(input.username);
+  if (!existingUser) {
+    throw new AuthenticationError("User does not exist");
+  }
+
+  const validPassword = await authService.verifyPassword(
+    existingUser.passwordHash,
+    input.password,
+  );
+  if (!validPassword) {
+    throw new AuthenticationError("Incorrect username or password");
+  }
+
+  return await authService.createSession(existingUser);
+}